provenance research on 14th-century greenwares found in singapore

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Stulemeijer: Provenance Research on 14th-Century Greenwares Found in Singapore NSC Working Paper No. 9 6.6. Scanning Electron Microprobe Analysis SEM works on the same physical basis as the XRF method. To stimulate the electrons in the atoms, an energetic beam of electrons from an ‘electron’ gun is directed onto the surface of the sample in a vacuum. Samples for this method have to be specially prepared. Either they have to be a thin polished section or perfectly flat carbon- or gold-coated, mounted specimens. This method is destructive. Scanning electron microscopes are usually easily available in an archaeological laboratory and typically used to study metal and ceramic technology (Sproto 2003). 6.7. Proton Induced X-Ray Emission PIXE is an extension of the emission of characteristic X-rays. It works by exciting the electrons using a beam of proton from a particular accelerator. The range of analytical possibilities is similar to that of SEM but this method is more suited to testing very small areas of light materials, for example layers of pigments or paper or the soldering of alloys in making jewellery (Sproto 2003). 6.8. Neutron Activation Analysis NAA excites the nucleus of an atom by making it radioactive. The energy that the atom radiates through gamma radiation is characteristic for each element. This was a frequently used method to analyse trace elements in ceramics and metal. This is a destructive method as samples are taken from the interior of the artefact by drilling. Tests are then done on these samples by using a nuclear reactor. As this technique involves the use of a nuclear reactor, only certain laboratories have this capability. With the closing down of nuclear reactors, these <strong>research</strong> laboratories have become rare (Sproto 2003). None exists in Singapore. For the purpose of this paper, I will concentrate on EDXRF testing on ceramics. Apart from its ready availability, it has the added advantage of being non-destructive to the artefacts and the process is relatively fast. I will also discuss my own EDXRF <strong>research</strong> where I tested Greenware ceramic materials, particularly from Asia. 24
Stulemeijer: Provenance Research on 14th-Century Greenwares Found in Singapore NSC Working Paper No. 9 7. How has EDXRF been used EDXRF was developed in the early 1970s. It uses a Lithium drifted or germanium detector so that it can detect almost the entire spectrum of chemical elements in an object simultaneously. A computer attached to the machine then registers the complex method of detection of the individual x-rays. As mentioned earlier, EDXRF can analyse a small area of 1mm diameter as well as objects of all shapes and sizes. A scientific method of testing, EDXRF is a non-destructive and reliable method of examining an object’s chemical composition. EDXRF can, when used on a small area (e. g. 1mm 2 ), give exact measurements but when one is measuring a larger areas (>1mm 2 ) the measurements are more geared towards an average of the chemical array in that specific area, a relative concentration one could say. The testing of a larger area is preferred, as EDXRF will average out the data, which means less chance that anomalies will have a major impact on the collected data. In addition, the larger the area the better the data will represent the whole artefact, which will give a better dataset for future comparisons. As a bulk characterization technique, EDXRF can rapidly and simultaneously detect chemical elements in an object that is heavier than fluorine (F9). By studying the trace or minor chemical elements in artefacts, EDXRF can contribute to the chemical fingerprinting of archaeological ceramics. With enough <strong>research</strong>, this chemical characterisation will identify the ceramics as being produced from a particular site. The definition of chemical fingerprinting according to Integral Consulting Incorporated; Chemical fingerprinting describes the use of a unique chemical signature, isotopic ratio, mineral species, or pattern analysis to identify or distinguish different chemical sources, reconstruct historical or ongoing loading patterns, date a particular event, or address causation or toxicity concerns 5 . However, source materials must be identified as well, so that the artefact’s chemical fingerprints can be compared and recognised, which then can lead to <strong>provenance</strong> 5 http://www.integral-corp.com/page.phppname=capabilities/forensics/1 25
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